Drilling technology has progressed to a highly robust level such that it is possible to reach petroleum, oil, or natural gas deposits which are 35,000 feet or more below the earth's surface. Such long shafts may also be used with a drilling process which deviates by design from a vertical path to reach hydrocarbons which are situated below locations which are either difficult to place a drilling rig on, populated, or environmentally sensitive. Unfortunately, despite improved drilling capability and the environmentally helpful flexibility in selecting a drilling location which such new technology affords, there are still facets of the drilling process which could be improved to reduce their impact on the environment.
Existing oil and gas drilling processes can take as little as two weeks, but the environmental impact may last for years. FIG. 1 schematically illustrates a typical existing oil or gas drilling process. A drilling rig 30 drives a drill bit 32 into the earth, aided by rotary torque and the compressive weight of drill extensions 34 and drill collars 36 above it. A drill pipe 38 is fed along with the drill bit 32 as it advances into the earth. Water is pumped down 40 the inside of the drill pipe 38 and exits 42 at the drill bit 32, helping to break up the rock, keep pressure on top of the bit 32, as well as cleaning, cooling, and lubricating the drill bit 32. Drilling debris is swept up 44 by the drilling water as it circulates back to the surface outside the drilling pipe. The water used for drilling can be industrial or potable water and depending on the location of the drilling site, the water may be supplied by a temporary connection to a municipal water supply, a well, or a reservoir. The drilling water may also be supplied by transporting the water to the drilling site in barrels and storing it on-site in a storage container 46 until needed.
The drilling fluid which returns to the surface is often referred-to as “mud” or “sludge”, and may contain a wide variety of contaminants. In addition to materials such as rock and sand, there are a variety of hydrocarbons such as oil and petroleum present in the drilling fluid. There is often a high salt content of the drilling fluid which returns to the surface due to the earth's composition where the drilling takes place. The salt content of the drilling fluid can often be near or even higher than an average salinity found in the ocean. (approximately 35 parts per thousand). Furthermore, the drilling sludge has been found to contain toxins and heavy metals which also contaminate the sludge.
A common practice to deal with the drilling sludge is to package the sludge in barrels 48 for transport to and disposal of in another location. When the two-week drilling process has concluded, the well can be capped-off and the area around the well may show little impact of the drilling team and equipment which were once there for a short time. However, there is still the drilling sludge to consider. The average drilling process can generate 300,000 barrels of sludge per day over a two week period, or the equivalent of 4,200,000 barrels of sludge for each drilled well. The sludge in these barrels is commonly disposed-of by returning it below the earth's surface by means of an insertion well, which unfortunately has the potential to pollute an area of land around the insertion well, in addition to possibly contaminating ground water supplies in the area.
Some drilling companies try to alleviate the environmental impact of sludge disposal by running the sludge through reverse osmosis filters to reclaim some of the water. Unfortunately, the reverse osmosis filters are limited to reclaiming only about 50% of the water which was originally used in the drilling process, the hydrocarbons in the sludge quickly plug-up the membranes of the reverse osmosis filters, and the remaining sludge is still disposed of in an insertion well or otherwise buried in the ground where it can pollute the land and the groundwater.
Other drilling companies have set-up treatment areas for oil-based components such that the oil based components are in the treatment area with added microorganisms which are seeded into the oil. While there certainly exist microorganisms which like to feast on oils, simply seeding the drilling sludge and allowing the microorganisms to float around in the sludge does not provide consumption of the oil at a rate which will make an impact on reducing the oil. While aeration may help such a seeded oil setup, the microorganisms will quickly become mature and their consumption rate slows down even further. It is common to find prior art oil treatment areas using microorganisms where the treatment areas are either stagnant, or had gentle mixing flows. For example, as noted in U.S. Pat. No. 5,228,998 which discloses a method of using biological microorganisms to remove selected biodegradable materials from a pond, heavy turbulence of the input stream is intentionally avoided . . .” (see col. 2, lines 64-65) and that “our invention achieves the biological activity that it uses to reduce pollutants by specifically avoiding uncontrolled turbulence in water being treated . . .” (see col. 2, lines 31-34). Unfortunately, devices like the one referred to in the '998 patent often tend to become clogged due to uncontrolled microorganism growth, and even when they are not clogged, they are not very efficient. The '998 patent also teaches that a flow rate of greater than 0.5 feet per minute will lead to disastrous results.
Therefore, it is desirable to have a method and system which can be used to treat the diverse components of the drilling sludge liquid in such a way as to substantially render the components harmless in an efficient, cost-effective, and environmentally friendly way.